1. Field of the Invention
This invention relates to marine propulsion. More particularly, it relates to a stern drive propulsion unit which may be powered by a single inboard or outboard engine.
2. Description of the Prior Art
It is well known that a single propeller propulsion unit, whether driven by an inboard or outboard engine, particularly in the higher horsepower ranges, produces undesirable torque and steering characteristics. These require the introduction of offsetting hull and trim features which are not only complex and bulky but also difficult to control in that they are optimum at only one specific design speed. Such offsetting hull and trim features are further undesirable because of their molded-in-hull features, particularly where both single and dual-engine installations of varying horsepower are offered in the same basic hull design. This is at least partly because lower horsepower single-engine, single propeller installations are generally over-corrected. Thus, the maximum horsepower for which currently available hulls are being marketed is being accomodated by the use of dual-engines and dual propellers. This entails considerable extra expense since it requires dual controls, instrumentation and an extra engine and drive unit. Furthermore, a dual-drive unit such as that of U.S. Pat. No. 2,936,730 splits into two drives above the water, steers with hydraulic power, and has no fail-safe mechanism. That is, if the lines are blocked, all steering will fail or become rigidized in opposing directions since hydraulically powered steering of that design is integral with each drive unit and lacks mechanical interconnection to preserve directional alignment of the drive units.